FIG. 1 is a flow chart depicting a conventional method 10 for fabricating a conventional perpendicular magnetic recording (PMR) transducer. For simplicity, some steps are omitted. The conventional method 10 is used for providing a PMR pole. An intermediate layer, chemical mechanical planarization (CMP) stop layer and hard mask layer are provided, via step 12. The intermediate layer is typically aluminum oxide. The CMP stop layer may include Ru, while the hard mask layer may include NiCr. A photoresist mask is provided on the hard mask layer, via step 14. The photoresist mask includes an aperture above the portion of the intermediate layer in which the PMR pole is to be formed. A conventional aperture is formed in the hard mask layer, via step 16. Typically, this is accomplished through using a conventional ion mill. Step 16 also includes forming a conventional aperture in the CMP stop layer. Thus, through ion milling in step 16, the pattern of the photoresist mask is transferred to both the hard mask and the CMP stop layer in a conventional manner.
Using the hard mask and photoresist mask, a trench is formed in the aluminum oxide layer, via step 18. Step 18 is typically performed using an alumina reactive ion etch (RIE). The top of the trench is desired to be wider than the trench bottom. In addition, the trench may extend through the aluminum oxide intermediate layer. As a result, the PMR pole formed therein will have its top surface wider than its bottom. Consequently, the sidewalls of the PMR pole have a reverse angle. The conventional PMR pole materials are deposited, via step 20. Step 20 may include plating or sputtering ferromagnetic pole materials as well as seed layer(s). A CMP is then performed, via step 22. The stop layer provided in step 12 is used to terminate the CMP.
Bevel(s) may also be provided in the conventional PMR pole, via step 24. If a top bevel is to be provided, step 24 may include removing a top portion of the ferromagnetic pole materials in the region of the air-bearing surface (ABS). As a result, the top surface of the conventional PMR pole near the ABS is lower than the yoke portion of the PMR pole. If step 24 is to be used to form a bottom bevel, the step 24 is typically performed earlier in the method 10, for example prior to step 20. In such a case, step 24 may include masking a portion of the trench formed in step 18 and refilling the bottom of the trench near the ABS region. As a result, a bottom bevel may be formed. Thus, the conventional PMR pole is provided. Subsequent structures, such as a write gap and shields, may then be provided.
Although the conventional method 10 may provide the conventional PMR transducer, there may be drawbacks. Use of the photoresist mask and hard mask may result in relatively large variations in the critical dimension of the conventional PMR pole. The critical dimension corresponds to the track width of the conventional PMR pole. Such variations in track width may adversely affect fabrication and performance. In addition, the conventional PMR pole may be relatively large in size. Using conventional photolithography, the critical diameter of the apertures formed in step 16, and thus the trench provided in step 18, is typically greater than one hundred fifty nm. Consequently, without more, the conventional PMR poles formed using the conventional method 10 may not be usable in high density magnetic recording technology.
Accordingly, what is needed is an improved method for fabricating a PMR transducer.